Heterixalus carbonei, Vences, Glaw, Jesu & Schimmenti, 2000

Griep, Stine & Glos, Julian, 2020, Description of tadpoles of the frogs Heterixalus tricolor, H. carbonei and H luteostriatus (Anura: Hyperoliidae) from western Madagascar, Zootaxa 4767 (2), pp. 332-344 : 338-340

Heterixalus carbonei

The description of the external morphology is based on a specimen in stage 31, field number 61HiwaB7.3.01, from Kirindy Forest (TL 22.56 mm, BL 7.63 mm; Table 1-2 , Fig. 2 ).

External morphology. In the dorsal view, the body has an ovoid form. Its widest point lies in the distal half to three quarters of the body. The snout is broadly rounded. In profile, the body is slightly depressed (BW 113% of BH). Its maximal height is in its distal half shortly behind mid-body. The snout is pointed. The eyes are moderately sized (ED 14% of BL) in a lateral position with dorsolateral orientation, and visible in the ventral view. Nares are located dorsolaterally, closer to the snout than to the eyes. They have a dark spot on their back and open both dorso- and anterolaterally in a round opening form. The distance between nostrils is about one quarter of the inter-orbital distance (NN 26% of IOD). The spiracle is sinistral and visible in the dorsal view. Its opening is located at maximum body width, shortly below the level of the proximal end of the tail myotomes axis. The spiracle opens posterodorsally, and its inner wall is free from the body. The vent tube is dextral, very short, and detached from the ventral fin. The coiled gut is visible. The tail is twice as long as the body (TAL 196% of BL). The tail muscle is narrow (TMW 32% of BW) and low (TMH 49% of BH). It rapidly converges (TMHM 22% of THM) until it reaches the pointed tail tip. Dorsal and ventral fins originate pointed at the body tail junction. The dorsal fin diverges to maximum height in the proximal quarter to half of the tail and starts converging towards its pointed tail tip in the distal quarter to half. The ventral fin reaches the comparably lower maximum height in the proximal quarter. Fin forms result in a tail that is at its maximum, which is in the proximal quarter to half of the tail (THM 67% of MTH), as high as the body (MTH 97% of BH).

The oral disc type is generalized without emargination and of moderate size (ODW 41% of BW). Its position and orientation are anteroventrally. On the lower labium, there is a single row of very few marginal papillae. Ventrally and laterally, there are some submarginal papillae. The longish and rounded papillae form a moderately sized dorsal gap (DG 55% of ODW). The LTRF is 1/3(1), P3 is much shorter than P1 and P2. Labial teeth have three to four cusps. The upper tooth row has at least half the width of the oral disc (A1 51% of ODW). The same is true for the jaw sheaths (JL 59% of ODW). The jaws sheaths are half keratinized with pointed serrations on their edges. The upper jaw sheath has a broad, arched form, while the lower one is V-shaped.

Coloration in preservative. Laterally, the tadpole is faintly pigmented in the anterior half and strongly pigmented in the posterior half. The coiled gut is visible. Dorsally, there is a broad strip of pigmentation that forks anteriorly. The fins and the lateral tail muscle show sparse pigmentation with a web of fine brown lines on the muscle and the dorsal fin. The limb buds are without pigmentation as well as the spiracle, which is transparent. The eyes are black. Ventrally, there is hardly any pigmentation, including the oral disc, which has dark brown pigments solely on the keratinized part of the jaws sheaths and the labial teeth.

Variation. The external morphology and general appearance was very similar between specimens. The ratios taken on five tadpoles in stages 27 to 31 vary in the following proportions: BH 104-133% of BW; ED 12-14% of BL; NN 24-46% of IOD; TAL 168-196% of BL; TMW 22-31% of BW; TMH 31-49% of BH; TMHM 21-28% of THM; THM 71-89% of MTH; MTH 68-97% of BH; DF 121-196% of TMHM; VF 126-177% of TMHM; DF 95 116% of VF; ODW 31-41% of BW; DG 39-55% of ODW; A1 51-61% of ODW; JL 51-59% of ODW.

Figures

FIGURE 2. Tadpole of Heterixalus carbonei in (A) the lateral and (B) the dorsal view, its oral disc (C) under the scanning electron microscope, (D) labial teeth from P1.